The present invention is directed toward a screw-type aggregate and fine material washer also known as dewaterers or classifers. Screw washers have a variety of functions from removing excess water from sand, and washing sand to remove slimes, silt and clays. Screw washers are built to various diameters and lengths, as well as single and double screw designs. The water volume in feed slurry varies with the requirements of the materials as well as the speed for turning the screw, and also the tolerance between the walls of the tank and the screw. The material being treated is fed into the lower end of the washer which contains a slurry, while the turning screw moves the material towards the opposite discharge end of the washer which is normally elevated. The bottom of the washer has an arcuate surface in close proximity to the spiral-shaped screw which is sometimes referred to as a belly pan. The tolerance between the screw and the belly pan is quite close in a dewatering application wherein the sand is squeezed between the wear shoes on the screw and the belly pan of the washer. Due to the abrasive affect on the screw, it is quite often necessary to adjust the position of the screw in the washer to attain the optimum clearance for the particular sand or gravel being treated. The concept of replaceable wear shoes on the screw has long been known in the prior art as well as the use of rubber or other abrasion resistant shoe materials.
The standard screw is made up from a heavy gauge steel pipe having continuous spiral screw flights welded to the pipe from one end to the other. The screw support bearings of most washers, at the tub or lower end of the washer, are normally submersible type bearings, within the slurry tank. Some of the prior art washers teach a method of vertically adjusting the support bearing so that the clearance between the screw and the belly pan of the tank can be adjusted at one end only.